api.versioning 版本控制 自动识别最高版本
Microsoft.AspNetCore.Mvc.Versioning //引入程序集
.net core 下面api的版本控制作用不需要多说，可以查阅https://www.cnblogs.com/dc20181010/p/11313738.html
普通的版本控制一般是通过链接、header此类方法进行控制，对ApiVersionReader进行设置，例如
services.AddApiVersioning(o => { //o.ReportApiVersions = true;//返回版本可使用的版本 o.ApiVersionReader = ApiVersionReader.Combine(new HeaderApiVersionReader("api-version"), new QueryStringApiVersionReader("api-version"));//通过Header或QueryString进行传值来判断api的版本
//o.DefaultApiVersion = new ApiVersion(1, 0);//默认版本号
});或者使用https://www.cnblogs.com/tdfblog/p/asp-net-core-api-versioning.html这种方式
这两种方式都需要传递api的版本信息，如果不传递将会报错
{"error":{"code":"ApiVersionUnspecified","message":"An API version is required, but was not specified.","innerError":null}}如果我们不想传递api的版本信息时，可以将
o.AssumeDefaultVersionWhenUnspecified = true; //此选项将用于在没有版本的情况下提供请求
o.DefaultApiVersion = new ApiVersion(1, 0); //设置默认Api版本是1.0
打开，这个我们每次请求如果不传递版本信息也不会报错了，但我们的请求将会指向1.0版本，那么我想让默认版本指向我写的api里面的最高版本怎么做？
我们将默认版本修改为最高版本可以吗？
这里将会出现一个问题，我的api版本可能由于各种各样原因造成最高版本不一致的问题
所以我们不能采用指定默认版本是最高版本的方法来解决，这个最高版本还必须要是动态的，通过翻阅https://github.com/microsoft/aspnet-api-versioning/wiki/API-Version-Selector#current-implementation-api-selector可以得知
The CurrentImplementationApiVersionSelector selects the maximum API version available which does not have a version status.
If no match is found, it falls back to the configured DefaultApiVersion. For example, if the versions "1.0", "2.0", and "3.0-Alpha" are available,
then "2.0" will be selected because it's the highest, implemented or released API version.CurrentImplementationApiVersionSelector选择不具有版本状态的最大可用API版本。 如果找不到匹配项，它将回退到配置的DefaultApiVersion。
例如，如果提供版本“ 1.0”，“ 2.0”和“ 3.0-Alpha”，则将选择“ 2.0”，因为它是最高，已实施或已发布的API版本。
services.AddApiVersioning( options => options.ApiVersionSelector = new CurrentImplementationApiVersionSelector( options ) );
通过这个版本选择器，我们可以将最大版本得出，修改上面services.AddApiVersioning
services.AddApiVersioning(o => { o.ReportApiVersions = true;//返回版本可使用的版本 //o.ApiVersionReader = new UrlSegmentApiVersionReader(); //o.ApiVersionReader = ApiVersionReader.Combine(new HeaderApiVersionReader("api-version"), new QueryStringApiVersionReader("api-version")); //o.ApiVersionReader = ApiVersionReader.Combine(new QueryStringApiVersionReader("api-version")); o.ApiVersionReader = ApiVersionReader.Combine(new HeaderApiVersionReader("api-version"));//版本号以什么形式，什么字段传递 o.AssumeDefaultVersionWhenUnspecified = true;//此选项将用于在没有版本的情况下提供请求 o.DefaultApiVersion = new ApiVersion(1, 0);//默认版本号 o.ApiVersionSelector = new CurrentImplementationApiVersionSelector(o);//默认以当前最高版本进行访问 });举个栗子
namespace Default.v1.Controllers{ [ApiVersion("1.0")] [Route("[controller]/[action]")] [ApiController] public class HomeController : Controller, IBaseController { private readonly ILogger<HomeController> _logger; public HomeController (ILogger<HomeController> logger) { _logger = logger; } public JsonResult GetJson() { return Json("Home 1.0"); }}Default.v1.Controllers.Homenamespace Default.v2.Controllers{ [ApiVersion("2.0")] [Route("[controller]/[action]")] [ApiController] public class HomeController : Controller, IBaseController { private readonly ILogger<HomeController> _logger; public HomeController (ILogger<HomeController> logger) { _logger = logger; } public JsonResult GetJson() { return Json("Home 2.0"); }}Default.v2.Controllers.Homenamespace Default.v1.Controllers{ [ApiVersion("1.0")] [Route("[controller]/[action]")] [ApiController] public class TestController : Controller, IBaseController { private readonly ILogger<HomeController> _logger; public TestController (ILogger<HomeController> logger) { _logger = logger; } public JsonResult GetJson() { return Json("Test 1.0"); }}Default.v1.Controllers.Test
我们在
请求/home/getjson 时返回“Home 2.0”
请求/test/getjson 时返回“Test 1.0”
这样就可以动态的请求最高版本了
但是还是会有问题的，比如，在我添加了Area和User区域下的HomeController，且User区域下的HomeController增加了1.0和3.0版本之后，神奇的一幕出现了
我的HomeController进不去了。。。
{"error":{"code":"UnsupportedApiVersion","message":"The HTTP resource that matches the request URI 'https://localhost:44311/home/getjson' is not supported.","innerError":null}}这个时候去google都查不到原因。。。
查看api-supported-versions，返回的是1.0,2.0,3.0。。。我的api版本控制被污染了3.0版本从哪里来的哪？第一反应是从User区域来的
我现在在User区域下添加一个除了Home和Test以外Name的Controller就可以请求成功，这个让我怀疑到是不是api.versioning本身的问题，首先怀疑的是Controller的Name问题，源码拉取下来，从添加版本控制的地方(services.AddApiVersioning)开始找
最后终于在ApiVersionCollator中找到了蛛丝马迹
///https://github.com/microsoft/aspnet-api-versioning/blob/master/src/Microsoft.AspNetCore.Mvc.Versioning/Versioning/ApiVersionCollator.csnamespace Microsoft.AspNetCore.Mvc.Versioning{ using Microsoft.AspNetCore.Mvc.Abstractions; using Microsoft.AspNetCore.Mvc.Controllers; using Microsoft.Extensions.Options; using System; using System.Collections.Generic; using System.Linq; /// <summary> /// Represents an object that collates <see cref="ApiVersion">API versions</see> per <see cref="ActionDescriptor">action</see>. /// </summary> [CLSCompliant( false )] public class ApiVersionCollator : IActionDescriptorProvider { readonly IOptions<ApiVersioningOptions> options; /// <summary> /// Initializes a new instance of the <see cref="ApiVersionCollator"/> class. /// </summary> /// <param name="options">The current <see cref="ApiVersioningOptions">API versioning options</see>.</param> public ApiVersionCollator( IOptions<ApiVersioningOptions> options ) => this.options = options; /// <summary> /// Gets the API versioning options associated with the collator. /// </summary> /// <value>The current <see cref="ApiVersioningOptions">API versioning options</see>.</value> protected ApiVersioningOptions Options => options.Value; /// <inheritdoc /> public int Order { get; protected set; } /// <inheritdoc /> public virtual void OnProvidersExecuted( ActionDescriptorProviderContext context ) { if ( context == null ) { throw new ArgumentNullException( nameof( context ) ); } foreach ( var actions in GroupActionsByController( context.Results ) ) { var collatedModel = CollateModel( actions ); foreach ( var action in actions ) { var model = action.GetProperty<ApiVersionModel>(); if ( model != null && !model.IsApiVersionNeutral ) { action.SetProperty( model.Aggregate( collatedModel ) ); } } } } /// <inheritdoc /> public virtual void OnProvidersExecuting( ActionDescriptorProviderContext context ) { } /// <summary> /// Resolves and returns the logical controller name for the specified action. /// </summary> /// <param name="action">The <see cref="ActionDescriptor">action</see> to get the controller name from.</param> /// <returns>The logical name of the associated controller.</returns> /// <remarks> /// <para> /// The logical controller name is used to collate actions together and aggregate API versions. The /// default implementation uses the "controller" route parameter and falls back to the /// <see cref="ControllerActionDescriptor.ControllerName"/> property when available. /// </para> /// <para> /// The default implementation will also trim trailing numbers in the controller name by convention. For example, /// the type "Values2Controller" will have the controller name "Values2", which will be trimmed to just "Values". /// This behavior can be changed by using the <see cref="ControllerNameAttribute"/> or overriding the default /// implementation. /// </para> /// </remarks> protected virtual string GetControllerName( ActionDescriptor action ) { if ( action == null ) { throw new ArgumentNullException( nameof( action ) ); } if ( !action.RouteValues.TryGetValue( "controller", out var key ) ) { if ( action is ControllerActionDescriptor controllerAction ) { key = controllerAction.ControllerName; } } return TrimTrailingNumbers( key ); } IEnumerable<IEnumerable<ActionDescriptor>> GroupActionsByController( IEnumerable<ActionDescriptor> actions ) { var groups = new Dictionary<string, List<ActionDescriptor>>( StringComparer.OrdinalIgnoreCase ); foreach ( var action in actions ) { var key = GetControllerName( action ); if ( string.IsNullOrEmpty( key ) ) { continue; } if ( !groups.TryGetValue( key, out var values ) ) { groups.Add( key, values = new List<ActionDescriptor>() ); } values.Add( action ); } foreach ( var value in groups.Values ) { yield return value; } } static string TrimTrailingNumbers( string? name ) { if ( string.IsNullOrEmpty( name ) ) { return string.Empty; } var last = name!.Length - 1; for ( var i = last; i >= 0; i-- ) { if ( !char.IsNumber( name[i] ) ) { if ( i < last ) { return name.Substring( 0, i + 1 ); } return name; } } return name; } static ApiVersionModel CollateModel( IEnumerable<ActionDescriptor> actions ) => actions.Select( a => a.GetApiVersionModel() ).Aggregate(); }}View Code
其中GroupActionsByController将Controller按照Controller的名字进行分组，再看看内部，分组的时候将GetControllerName( action )作为key，那么GetControllerName是干嘛的，
protected virtual string GetControllerName( ActionDescriptor action ) { if ( action == null ) { throw new ArgumentNullException( nameof( action ) ); } if ( !action.RouteValues.TryGetValue( "controller", out var key ) ) { if ( action is ControllerActionDescriptor controllerAction ) { key = controllerAction.ControllerName; } } return TrimTrailingNumbers( key ); }这个方法原本是没有问题的，但是牵扯到Area的时候就会出问题了。。它将根目录下的HomeController和User.HomeController视为同一类的Controller然后去做版本的属性注入，造成CurrentImplementationApiVersionSelector选择器选不到正确的版本，所以返回了上面的错误，我们将GetControllerName内部修改为
protected virtual string GetControllerName( ActionDescriptor action ) { if ( action == null ) { throw new ArgumentNullException( nameof( action ) ); } if ( !action.RouteValues.TryGetValue( "controller", out var key ) ) { if ( action is ControllerActionDescriptor controllerAction ) { key = controllerAction.ControllerName; } } if ( !action.RouteValues.TryGetValue( "area", out var area ) ) { } return TrimTrailingNumbers( area + key ); }这样就可以走通了
我们有两种解决办法，一个是把源码拉取下来，方法修改掉，项目的依赖项替换为自己修改的Microsoft.AspNetCore.Mvc.Versioning，另一种办法是将services.AddApiVersioning重写。。。请相信我，拉取修改替换依赖比重写services.AddApiVersioning快且简便。。。
issue：https://github.com/microsoft/aspnet-api-versioning/issues/630
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